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Unformatted text preview: ECE190 Exam 1, Fall 2008 Thursday 25 September Name: Be sure that your exam booklet has 9 pages. The exam is meant to be taken apart! Write your name at the top of each page. This is a closed book exam. You may not use a calculator. You are allowed one 8 . 5 11 &quot; sheet of handwritten notes. Absolutely no interaction between students is allowed. Challenging problems are marked with ***. Show all of your work. Dont panic, and good luck! ...there would be no more wars, the nations were so economically interdependent. S. Foster Damon, remembrance ca. 1912 Problem 1 20 points Problem 2 20 points Problem 3 10 points Problem 4 25 points Problem 5 25 points Total 100 points Name: ____________________________________________ 2 Problem 1 (20 points): Short Answers Please answer concisely. If you find yourself writing more than a few words or a simple drawing, your answer is probably wrong. Part A (5 points): Using an 8-bit 2s complement data type, what is the smallest positive number that generates an overflow when added to itself? Part B (5 points): How many positive integers are represented in a 13-bit 2s complement data type? Part C (5 points): Using one or more LC-3 instructions, implement a branch if positive (BRp) to an address outside the range of the branch instruction. Assume that the address to which you want to branch is stored in R5. Write your instruction(s) in binary. Note: you may not need all the lines provided below. Address Instruction x3000: ______________________________ x3001: ______________________________ x3002: ______________________________ x3003: ______________________________ Part D (5 points): The current LC-3 memory contains a total of 1 Megabit (2 20 bits). If we were to make the memory byte-addressable (a byte is 8 bits) without changing its size, and without changing the size of the instructions (16 bits), how many bits would be necessary in the following registers? MAR IR Name: ____________________________________________ 3 Problem 2 (20 points): Logic Circuits Part A (3 points): Using exactly one logic gate whose inputs are not inverted, draw a logically equivalent circuit to the one pictured below. Part B (3 points): Using exactly one logic gate whose inputs are not inverted, draw a logically equivalent circuit to the one pictured below....
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